This invention relates to the construction of electroluminescent display devices having a light emitting electroluminescent panel electrically coupled to an electronic circuit board, and in particular to a construction and method of fabrication of such panels that makes use of a novel framing technique that is efficient and cost effective.
Traditionally, electroluminescent (EL) display devices have been constructed by compressing together a light emitting EL panel, an elastomeric connector, and an electronic circuit board in a sheet metal frame. A foam gasket between the sheet metal frame and the light emitting EL panel provides the compression force to squeeze together the light emitting EL panel, the elastomeric connector, and the electronic circuit board. A rigid spacer positions the elastomeric connector and determines a compressed thickness. A desirable object in the design of EL display devices is for them to be as thin as possible, but the gasket and the sheet metal frame add to the thickness of the fully constructed device.
The prior method of constructing such EL display devices requires a large, complicated machine to assemble the components. The machine aligns the light emitting EL panel and electronic circuit board, compresses the components together, and bends tabs on the sheet metal frame to hold the components together. The compression force is provided by an air cylinder above the light emitting EL panel. The air cylinder is usually oriented vertically, thus requiring substantial vertical clearance above the assembling machine.
The prior method of constructing EL display devices also requires precise dimensions for each component part. EL display devices need a reliable electrical connection between the light emitting EL panel and the electronic circuit board. The prior method of constructing EL display devices maintained the electrical connection by using a foam gasket to compress an elastomeric connector between the light emitting EL panel and the electronic circuit board. If the combined thickness of the foam gasket, EL panel, elastomeric connector, and electronic circuit board is too thin, then the compression force provided by the foam gasket will be insufficient to maintain a reliable electrical connection between the light emitting EL panel and the electronic circuit board. However, if the combined thickness is too thick, it is difficult for the machine to compress the components together and bend the tabs on the sheet metal frame to hold the components together. Accordingly, the thickness of each component is critical to achieve both ease of assembly of the EL display device and a reliable electrical connection.
What is therefore desired is a construction and method of fabrication for an EL display device that is efficient, cost effective, maintains a reliable electrical connection between the light emitting EL panel and the electronic circuit board, and results in a thin EL display device.